This disclosure relates to methods and apparatus for use in forming subterranean boreholes, and more specifically to tools that bend or flex within such boreholes. Directional or steerable drilling tools can be employed to drill boreholes that deflect the bit path by some degree from an existing path into a subterranean formation, by imposing one or more (typically multiple) radii into the borehole path. In some cases, these radii will be difficult for other tools in the tool string, or in another tool string, to traverse.
Drilling systems that deploy a tool string in a non-linear borehole need segments of the string capable of navigating the non-linear portions of the borehole. As such, these tool string segments may be required to bend or otherwise conform to the radius or curved portion of the borehole. In some cases, the tool string segments are configured to bend to navigate the curved portions of the borehole. To achieve maximum deflection, such bending tool string segments are commonly configured to bend across their entire length, which generally may place the maximum stress at the central most region of the segment.